Stihl MS250 Oil Leak (no, not that one)

[nastiliusprime]

greetings,

I am here after a bit of a dead end in my research. My Stihl ms250 is leaking bar/chain oil as I cut as well as when it is sitting, but it is a steady drip as it cuts. In my research I have found and ruled out the set screw below the muffler as mine is intact.

I have taken off and cleaned clutch/bearings as well as oil pump. Everything appears in fine working order.

I have replaced oil line and filter, I did not replace O-ring sealing chamber leading to oil pump as I don't have piece but that does not seem to be where the leak is coming from.

The leak seems to be coming from where the bar meets the body, seemingly where the oil is pumped to meet hole in bar, obviously there should be oil here, but its dripping from here as I cut, instead of only pumping oil into bar. I wonder if this is related to oil vent (although a clogged oil vent seems to have been leading others to a lack of oil to bar, which i am not experiencing, so not sure) I dont have any compressed air at the moment but will try blowing out the vent once I get some and see if that helps the over-oiling.

Anyways I don't like spewing oil everywhere as I cut but have run into a dead end.
Could a worn bar be causing the leak? The oil hole in bar is fine but bar is on the older side.

What else could be causing a leak from this placement on the saw?

I have disassembled and reassembled many times and am now at a loss for why this leak is still occurring
Thanks in advance for any advice!

 

[PV Hiker]

Just to cover some basics...
The hole in the bar is clean?
The hole in the bar lines up with the oiler hole?
The bar is the right one for the saw?
The bar grove is clean of all dried up saw dust and oil so the drive links can move the oil down the bar grove?

Some pictures would help some see problems you can not.

 

[nastiliusprime]

Just to cover some basics...
The hole in the bar is clean?
The hole in the bar lines up with the oiler hole?
The bar is the right one for the saw?
The bar grove is clean of all dried up saw dust and oil so the drive links can move the oil down the bar grove?

Some pictures would help some see problems you can not.

Thanks for your reply.
The hole is as clean as I could get it without an air compressor.
The holes line up though they might not be flush, is there a specific method/tool to tighten the bar set screws? (to ultimately bring the bar closer to the oiler)

The bar is the correct one for the saw, though it is worn as you can see in pictures, i am getting a new one just trying to sort this out until it comes.

Attached are some pictures, hope that helps.

 

[HarleyT]

Yes, the bar needs to clamp tightly against the flat surface, the bar studs look a little raised, they screw in like any other screw, so you can double nut it and try to tighten. If they keep turning , then you may need to go the oversize option.

 

[SteveSr]

The bar is the correct one for the saw, though it is worn as you can see in pictures, i am getting a new one just trying to sort this out until it comes.

The bar rails look to be BADLY splayed to the point of un-usability. Clean it up good and take another look. If it is only bad on one side try putting that side on the bottom. Try measuring the bar with calipers and/or the bar groove with feeler gauges after cleaning.

 

[Bob Hedgecutter]

The bar rails look to be BADLY splayed to the point of un-usability. Clean it up good and take another look. If it is only bad on one side try putting that side on the bottom. Try measuring the bar with calipers and/or the bar groove with feeler gauges after cleaning.

Think he has figured that one out- "The bar is the correct one for the saw, though it is worn as you can see in pictures, i am getting a new one just trying to sort this out until it comes."
I agree though, the bar is toast.
I think Harley nailed it with the loose bar studs and the flange holding the bar above the plastic surrounds- leaving a void for the oil to fall down the face of the outlet housing without ever reaching the bar.

 

[nastiliusprime]

Yes, the bar needs to clamp tightly against the flat surface, the bar studs look a little raised, they screw in like any other screw, so you can double nut it and try to tighten. If they keep turning , then you may need to go the oversize option.

thanks for reply,
what do you mean by oversize option? as in bigger bar studs?
I was worried about torqing down on them w the nuts on as I have gotten them stuck before, in which case the studs come out with the nuts on the way out, but ill try to find that sweet spot and get them flush.

 

[nastiliusprime]

Think he has figured that one out- "The bar is the correct one for the saw, though it is worn as you can see in pictures, i am getting a new one just trying to sort this out until it comes."
I agree though, the bar is toast.
I think Harley nailed it with the loose bar studs and the flange holding the bar above the plastic surrounds- leaving a void for the oil to fall down the face of the outlet housing without ever reaching the bar.

cool thanks for diagnosis and reply,

I have read about these ms250s commonly having oil leak issues. Someone gave me this saw so I am fixing it up before putting it to work.

If a new bar and torquing bar studs does not solve leak has anyone heard of sucess with RTV or the like to better seal bar/oiler together?

Also, side note, has anyone had sucess running vegetable oil for chain oil? I heard they use it in germany and some people use it here. I will be doing a bunch of cutting up near my drinking water and don't like the taste of petroleum distillates all that much.

thanks again i appreciate all the helpful info

 

[PV Hiker]

Yes, the bar needs to clamp tightly against the flat surface, the bar studs look a little raised, they screw in like any other screw, so you can double nut it and try to tighten. If they keep turning , then you may need to go the oversize option.

thanks for reply,
what do you mean by oversize option? as in bigger bar studs?
I was worried about torqing down on them w the nuts on as I have gotten them stuck before, in which case the studs come out with the nuts on the way out, but ill try to find that sweet spot and get them flush.

Ö

If you have tried to tighten down the bar studs and they keep spinning, then yes you need a oversize stud that screws into the housing. @HarleyT can give you a number for that part. Once you get a new bar and the studs don't spin, the bar will sit against the housing making a seal for the oil to make its way into the bar grove.

Thank you so much for giving more details and especially for the images as that really helped giving you a answer a whole lot faster.

 

[HarleyT]

Here,
you ought to have this anyway..
Page 56....

 

[SEAM]

There is one more possible cause...

With this design, the engine unit sometimes will rattle loose causing the engine to slant and the drum/clutch to rub against and eat into the tank housing - can be seen easily when removing the sprocket. In the earl stages an easy fix using epoxy and the like and replacing the engine mount bushings with suitable new ones.
Good luck!

 

[mike-s]

as in bigger bar studs?

The part which threads into the plastic is oversized. Personally, I'd first reuse what you have by pulling the studs, cleaning the holes and studs well with degreaser, and re-installing them fully seated using a thread locker (Loctite). Once you go oversize, that option is gone. Oversized ones seem more suited to when they've basically pulled through the plastic threads. Your's seem to be unscrewing, not pulling out. But, maybe not - you should be able to feel how tight they thread in.

 

[stihl86]

You’re over analyzing things. You don’t need sealer. They don’t suffer from an abnormal amounts of leaks. The system is metered to over oil. All Stihl homeowner saws are. Replace the bar, locite the studs in tight. Make sure you can run the bar nuts finger tight.and see where you stand. Nuts must be free running.
And if you removed the pump, you might have created another problem.

As for vegetable oil. There’s no tackifers in it. It won’t lub ss well as petro based bar oil.
It get rancid after a while, gums things up and it stinks.
Stihl has bio oil which is prohibitive in the price.
Maybe you can find a less expensive alternative.
I’ve serviced many saws for ice carvers. Veggie oil is a pita.

 

[Bob Hedgecutter]

You’re over analyzing things. You don’t need sealer. They don’t suffer from an abnormal amounts of leaks. The system is metered to over oil. All Stihl homeowner saws are. Replace the bar, locite the studs in tight. Make sure you can run the bar nuts finger tight.and see where you stand. Nuts must be free running.
And if you removed the pump, you might have created another problem.

As for vegetable oil. There’s no tackifers in it. It won’t lub ss well as petro based bar oil.
It get rancid after a while, gums things up and it stinks.
Stihl has bio oil which is prohibitive in the price.
Maybe you can find a less expensive alternative.
I’ve serviced many saws for ice carvers. Veggie oil is a pita.

I sometimes use veggie oil in my 020 top handle........ but that is the saw I use to split beef carcasses in half down the backbone..........

 

[KiwiBro]

As for vegetable oil...It won’t lub ss well as petro based bar oil.

If rapeseed oil/canola is a 'vegetable' oil, you and my IR temperature reader will have to agree to disagree on that.

 

[HarleyT]

Olive oil is better for the saw's heart....

 

[L34]

Also good for Pop Eye.

 

[nastiliusprime]

You’re over analyzing things. You don’t need sealer. They don’t suffer from an abnormal amounts of leaks. The system is metered to over oil. All Stihl homeowner saws are. Replace the bar, locite the studs in tight. Make sure you can run the bar nuts finger tight.and see where you stand. Nuts must be free running.
And if you removed the pump, you might have created another problem.

OK. Ill do that and see how it goes. Pump is not problematic (unless its working too well/much) I cleaned well and made sure to reinstall properly.

As for running "bar nuts finger tight" so they are free running.
What do you mean they must be free running? As in not to overtighten so chain tensioner can still be adjusted? Or is there aditional reasoning these nuts need to be loose?

Thanks again for everyones contribution, I'm certainly happy I found this site and will be updating after all repairs are complete.

 

[stihl86]

If rapeseed oil/canola is a 'vegetable' oil, you and my IR temperature reader will have to agree to disagree on that.

Yes, we would. Or do they have a tackifer in them?

 

[stihl86]

OK. Ill do that and see how it goes. Pump is not problematic (unless its working too well/much) I cleaned well and made sure to reinstall properly.

As for running "bar nuts finger tight" so they are free running.
What do you mean they must be free running? As in not to overtighten so chain tensioner can still be adjusted? Or is there aditional reasoning these nuts need to be loose?

Thanks again for everyones contribution, I'm certainly happy I found this site and will be updating after all repairs are complete.

Um, same thread and 2 people cut my post and modified what I said.
2 separate statements about the bar nuts. Just make sure the threads on both the studs and nuts are OK.